Porous composite and its use for gas storage

Abstract

Porous composite and its use for gas storage This application relates to the storage of gases, by means of a porous composite based on a porous matrix and an organic compound confined in solid form within pores of the matrix with a diameter of less than 10 nm. Figure for abstract: None

Description

Title of the invention: Porous composite and its use for gas storage

[0001] The present invention relates to the field of energy storage and in particular the storage of gases, such as dihydrogen (H2).

[0002] Hydrogen is at the heart of tomorrow's ecological transition and is seen as one of the fuels of the future. Public policies and major energy players are positioning themselves strongly in this area. The means of storing H2 in the Hydrogen energy chain is a major obstacle to large-scale deployment.

[0003] There are different types of hydrogen storage, such as in conventional tanks (in gaseous or liquid form) and in solid form (in adsorbed, absorbed or trapped form). None of these techniques is, to date, completely satisfactory for stationary and mobile storage, whether for reasons of insufficient performance, safety, social acceptability, or profitability.

[0004] Solid storage is currently carried out:

[0005] either by adsorption in porous matrices but the storage capacities only prove interesting at very low temperatures, in particular at cryogenic temperatures (77K),

[0006] either by absorption in metal or complex hydrides. Even if some of them have an interesting storage volume density (higher than that of liquid hydrogen) and even if the pressures involved are moderate, the use of this type of material encounters two major drawbacks: the kinetics of hydride formation and dehydration are slow and the dehydration temperatures are high (above 300°C and 480°C for MgH2 and LiBH4 respectively).

[0007] FR 3000907 describes a reactive medium comprising a porous support on which is deposited in solid form an organic compound capable of forming gas clathrates, such that the porous support comprises pores with a size between 10 nm and 150 nm, preferably between 30 nm and 120 nm. After impregnation carried out in a liquid manner, the organic compound in solid form is deposited on the surface and / or within the pores of the support. The gas can be captured by the organic compound in the form of clathrates.

[0008] This technique has the disadvantage of using solvents, requiring dissolution, filtration and drying steps.

[0009] It therefore remains to provide a technique for storing dihydrogen with interesting storage capacities and allowing storage and release of the gas under easy conditions.

[0010] These aims are notably achieved by the present invention.

[0011] Thus, the present invention relates to a porous composite for gas storage comprising: - a porous matrix comprising pores with a diameter of less than 10 nm, and - an organic compound,

[0012] said porous composite being characterized in that said organic compound is present within said pores with a diameter of less than 10 nm.

[0013] For the purposes of the present invention, the term “composite” denotes the system consisting of at least two materials, namely a porous matrix and an organic compound.

[0014] The term “porous matrix” means a solid material comprising pores within which an organic compound can be deposited.

[0015] The porous matrices suitable within the framework of the invention can in particular be used in industrial processes, in particular for the storage and use of stored gases, and in particular, do not degrade under the temperature and / or pressure conditions implemented within these processes.

[0016] Advantageously, the porous matrix is ​​chosen from organic or mineral micro- and / or mesoporous supports, such as silica, carbon, alumina, alumino-silicates, activated carbons, molecular sieves, zeolites, organo-metallic structure materials (Metal Organic Frameworks, MOFs), Hofmann clathrates and polymers.

[0017] Preferably, the porous matrix may be chosen from mesoporous silicas MCM-41 and SBA-15, aluminosilicates, carbon xerogels, activated carbons and porous polymers.

[0018] According to the IUP AC nomenclature, “mesoporous” refers to pores with a diameter between 2 and 50 nm and “microporous” refers to pores with a diameter less than 2 nm.

[0019] The pore size can be measured by gas porosimetry with nitrogen or argon as the probe molecule. This technique consists of measuring the adsorption isotherm of the probe molecule at cryogenic temperatures (77K for nitrogen and 87K for argon generally) for pressures ranging from 107 bar to 1 bar. Thermodynamic models are then used, preferably Density Functional Theories (DFT) to deduce from these isotherms the pore volume and the pore size distribution of the porous matrices.

[0020] According to one embodiment, the matrix comprises a micro- or mesoporous volume, that is to say a volume defined by micropores and mesopores.

[0021] Thus, according to one embodiment, the pores of the porous matrix with a diameter of less than 10 nm represent at least 30%, preferably at least 50%, of the micro- / mesoporous volume of the porous matrix. This percentage is determined experimentally by a combination of analyses carried out by gas porosimetry (which makes it possible to characterize pores with a diameter of less than 30 nm), by mercury porosimetry (which makes it possible to characterize pores with a diameter of between 30 nm and several hundred micrometers), and by pycnometry (which makes it possible to evaluate the total pore volume).

[0022] Typically, porous matrix particles are used, such as beads, grains, pellets or fabrics for example, in particular silica beads or pellets, or grains, pellets or fabrics of activated carbon. Small porous particles will preferably be chosen, the characteristic dimension of which (the diameter for a spherical particle, the height of the cylinder for a pellet) varies, for example, between 30 μm and 10 mm.

[0023] According to one embodiment, the porous matrix has a high specific surface area, in particular between 200 m2 / g and 3000 m2 / g.

[0024] The organic compound is chosen from compounds capable of forming hydrogen bonds.

[0025] According to one embodiment, said bonds can be described as “intermolecular” in that they are formed between a molecule of organic compound and another molecule, typically between at least two molecules of the organic compound, or between a molecule of the organic compound and a molecule of the stored gas (for example hydrogen).

[0026] Thus, suitable organic compounds comprise one or more electronegative atoms carrying at least one non-bonding doublet, such as oxygen O, nitrogen N, fluorine F, chlorine Cl, bromine Br, iodine I.

[0027] According to one embodiment, the organic compound may in particular be chosen from the following families: polyphenols, polythiols, ureas, thioureas and calixarenes. In particular, said organic compound may be chosen from the group consisting of hydroquinone, resorcinol, fluorohydroquinone, 2-5 dihydroxyl-pyridine, catechol, urea, thiourea, calix[4]arene and mixtures thereof.

[0028] Preferably, the organic compound is hydroquinone.

[0029] According to one embodiment, said organic compound is present in condensed form within the pores. According to one embodiment, said organic compound may be present in crystalline, semi-crystalline and / or amorphous form within the pores of the porous matrix.

[0030] According to the invention, the organic compound can be deposited within the pores of small size, especially those with a diameter of less than 10 nm.

[0031] Preferably, said organic compound occupies a large portion of the pores of the porous matrix, and in particular of the micropores and mesopores of the porous matrix. Thus, according to one embodiment, said organic compound occupies at least 25%, preferably at least 40% of the micro- and mesoporous volume of the porous matrix.

[0032] According to one embodiment, the organic compound can occupy up to the entire pore volume of the porous matrix.

[0033] The volume percentage of pores occupied by said organic compound can be determined by gas porosimetry.

[0034] According to another object, the present invention also relates to a process for the dry preparation of a porous composite according to the invention, said process comprising the diffusion of organic vapors into the porosity of said porous matrix, followed by the adsorption / condensation of said organic compound within the pores of said porous matrix.

[0035] The process according to the invention is carried out “by the dry route”, that is to say without solvent.

[0036] The term "adsorption / condensation" refers to the change of state of the organic compound during the process.

[0037] Without wishing to be bound by theory, the physical mechanism of incorporation of the organic compound within the pores of the matrix is ​​based on adsorption, in particular by physisorption, or even chemisorption, involving in particular the formation of hydrogen or van der Waals type bonds, and the simultaneous condensation of the gas phase, hereinafter referred to as adsorption / condensation.

[0038] According to one embodiment, the condensation of the organic product takes place within the pores of the porous matrix.

[0039] More particularly, the organic compound in gaseous form condenses during adsorption within the pores of the matrix.

[0040] Within the composite of the invention, the organic compound confined within the pores is therefore present in condensed form.

[0041] The organic compound can be described here indifferently as an “impregnated”, “condensed” or “confined” compound and designates a homogeneous or inhomogeneous, solid and / or liquid state.

[0042] According to one embodiment, the organic compound in gaseous form can be obtained from its solid form by sublimation.

[0043] According to one embodiment, said method may therefore also comprise the prior step of sublimation of said organic compound from the solid phase to the gas phase. This sublimation step may typically be carried out at reduced pressure, under heating, for example under vacuum and at a temperature between 50 and 250°C.

[0044] According to one embodiment, the confinement of the hydroquinone can be carried out by a vacuum in order to sublimate it, in particular at a temperature between 80 and 170°C, followed by a return to room temperature.

[0045] Thus, the sublimed organic compound, in the gaseous state, penetrates into the pores of the porous matrix where it condenses / adsorbs in condensed form.

[0046] Said organic compound can thus be confined in the pores, after condensation, without decomposition or degradation.

[0047] The present invention also relates to a porous composite capable of being obtained by the method described above.

[0048] According to the invention, the composite thus obtained has the particularity of comprising a condensed organic compound confined within pores with a diameter of less than 10 nm of a porous matrix.

[0049] The porous composite described above makes it possible to store gases. According to another object, the present invention also relates to a method for storing gas, said method comprising: - bringing the porous composite according to the invention into contact with the gas to be stored or a mixture comprising said gas; - submission to one or more successive temperature cycles.

[0050] Typically, storage is achieved by the capture of the gas by the organic compound confined within the meso- or micropores of the matrix. The capture and then the retention of the gas are generally achieved by means of weak bonds, for example of the van der Waals type, established between the atoms of said organic compound and the hydrogen atoms of the gas.

[0051] The expression “temperature cycle” used here is understood as the successive passage from a temperature T1 to a temperature T2, such that T1 <T2.

[0052] According to one embodiment, Tl can be chosen from temperatures greater than or equal to 77 K, in particular 0°C.

[0053] According to one embodiment, T2 can be chosen from temperatures lower than the desorption temperature of the condensed organic compound, in particular approximately 100°C.

[0054] The pressure used during these cycles may be, for example, between 1 and 200 bar, preferably between 5 and 150 bar, advantageously between 20 and 120 bar.

[0055] One or more cycles may be successively applied. The number of cycles may vary depending on the nature of the matrix and the organic compound. Generally, a sufficient number of cycles is applied when the amount of incorporated organic compound reaches a plateau. This amount may be determined by measurements of adsorbed gas quantities carried out, for example, using gravimetric or volumetric techniques.

[0056] Advantageously, the composite according to the invention makes it possible to store dihydrogen.

[0057] According to another object, the invention also relates to the system consisting of the composite incorporating the stored gas capable of being obtained by the method according to the invention.

[0058] The invention therefore also relates to a gas storage device comprising the porous composite according to the invention and a gas, said gas being stored within the pores comprising the organic material.

[0059] Advantageously, the storage is stable under normal temperature and pressure conditions, for example at 25°C / 1 bar or at 0°C / 1 bar (CNTP).

[0060] According to another object, the present invention also relates to the use of this device, comprising the release of said gas at ambient pressure and at a temperature below 150°C.

[0061] The destocking is carried out by releasing the gas. This step is carried out at a temperature depending on the nature of the organic compound. Typically, the destocking is carried out at a temperature lower than the desorption temperature of the condensed organic compound.

[0062] Advantageously, in the case of hydrogen, the destocking of dihydrogen can be carried out at ambient pressure and at a temperature less than or equal to 150°C, in particular less than 100°C.

[0063] The present invention also relates to the use of the porous composite according to the invention for the storage of gas, in particular dihydrogen.

[0064] The storage of gas in the porous composite according to the invention has the advantage of being reversible. Indeed, if the destocking is carried out, the organic compound remains confined within pores and can again capture gas, in a manner identical to the previous capture reaction. In particular, the dihydrogen capture reaction is reproducible in terms of the quantity of gas captured. The composite according to the invention is therefore reusable once the gas has been desorbed.

[0065] According to another of its objects, the invention also relates to the use of the storage device according to the invention for the purpose of using the gas stored therein. According to the invention, the use therefore comprises the step of destocking said gas. Typically, the destocking can be carried out at a temperature lower than the temperature T2 mentioned above. In the case of hydroquinone, the destocking can be carried out at a temperature lower than 150°C, in particular lower than 100°C.

[0066] The invention will be better understood on reading the following description, given solely by way of example, and made with reference to the appended drawings, in which: Brief description of the drawings

[0067] [Fig.l] [Fig.l] illustrates a diagram of the impregnation device.

[0068] [Fig.2] [Fig.2] represents results obtained after impregnation of different porous matrices by hydroquinone (HQ). (A) Influence of impregnation time on the mass content of impregnated HQ (in %) for 3 carbon matrices (1 fibrous matrix called "fabric" and 2 activated carbons), 3 mesoporous matrices based on silica and a porous polymer. (B): TGA / DSC analysis showing that HQ is in the pores of MCM-41 silica (peak shift compared to solid HQ). (C) Analysis of the pore volume by argon porosimetry at 87 K before (grey curve) and after HQ impregnation (impregnation time: 8h) (black curve): 80% of the pore volume is occupied by HQ. (D) Pore size distribution by argon porosimetry at 87 K before (grey curve) and after HQ impregnation (black curve).

[0069] [Fig.3] [Fig.3] represents the evolution of the mass percentage of H2 captured (by total mass of material) as a function of temperature cycles varying between 0 and 100°C for MCM-41 impregnated with HQ (case of an impregnation duration of 8 h) (P=20 bars).

[0070] [Fig.4] [Fig.4] represents the mass percentage of H2 captured (per total mass of material) as a function of temperature cycles varying between 0 and 100°C for porous polymer beads (case of an impregnation time of 14 h) impregnated with HQ (P=20 bars). Examples: Preparation of the porous composite

[0071] The protocol is illustrated in [Fig.l]: 1. Between 1 and 5 g of solid organic compound (hydroquinone, HQ) is introduced into a crucible above which is placed another crucible containing the porous matrix to be impregnated (between 200 and 1000 mg) and previously purified under primary vacuum at a suitable temperature (200°C for carbons, 300°C for silicas and 120°C for the polymer) depending on the material. 2. The two crucibles are separated by a Durapore filter with a porosity of 0.45 qm. 3. The assembly is placed in a vacuum oven at 120°C for a period of time between 1 and 64 hours in order to sublimate the HQ and for it to adsorb inside the pores of the matrix placed above, in crystalline, semi-crystalline and / or amorphous form. The influence of the impregnation time was analyzed. 4. The system is then cooled (controlled temperature ramp) and returned to atmospheric pressure. Impregnation results:

[0072] The protocol was tested on micro / mesoporous adsorbents based on carbon and silica:

[0073] 1: Fabric

[0074] 2: G-Bac

[0075] 3: F400

[0076] 4: Porous polymer

[0077] 5: MCM-41

[0078] 6: SBA-15

[0079] 7: Si-Al

[0080] Fabric (PICA woven activated carbon from PICY Company, Levallois, FRANCE), G-bac (from Kureha®) and F400 (Filtrasorb®400 from Calgon Carbon Corporation) are carbon matrices.

[0081] MCM-41, SBA-15 and Si-Al are silica-based matrices referenced under these names. The porous polymer is Dow Chemicals' Optipore, newly referenced at Dupont).

[0082] The organic product used is hydroquinone (purity > 99.5%, from the supplier Acros Organics).

[0083] The maximum impregnation rates are reached after a few hours and are between 12 and 38% by mass depending on the support. Figure 2A illustrates the results obtained for the different matrices 1-7 identified above.

[0084] MEB, ATG / DSC analyses and gas porosimetry characterizations showed that the HQ was well impregnated within the porosity (see [Fig.2]). H2 capture tests

[0085] • H2 capture tests were carried out by gravimetric technique using of a magnetic suspension balance (Rubotherm).

[0086] • The influence of temperature and pressure was analyzed. A study ex exhaustive study of the hybrid material MCM-41 / HQ showed the following results:

[0087] - an initial temperature rise is necessary to “activate” the system, 80 °C for MCM-41,

[0088] - successive temperature cycles (from 0°C as minimum temperature to 100°C as maximum temperature for the example given in [Fig.3] i.e. MCM-41 / HQ allow on the one hand to capture / release H2 and on the other hand to reach a maximum capture rate after around ten cycles;

[0089] - the compound remains stable at ambient pressure for at least 48 hours;

[0090] - for the MCM-41 / HQ system, the mass percentage of H2 obtained at pressure at spherical and at 25°C ([Fig.3]) is approximately 1.2% by total mass of impregnated material or 5.7% by mass of HQ.

[0091] • Capture tests on a very different porous matrix (porous polymer with polystyrene-based, Optipore from Dow Chemicals) gave similar results ( [Fig.4]), which seems to show that the variability of nanoporous matrices (in terms of chemical nature and pore sizes) that can be used is large.

[0092] Comparison with existing solid H^ storage:

[0093] The H2 capture rate per mass of composite (1.2%) or per mass of HQ (5.7%) thus obtained is in the average of existing processes, with reference to the classification made for different existing solid storages by Gupta et al., Energy Storage Materials, vol. 41, p. 69-107, Oct. 2021.

[0094] Nevertheless, the system according to the invention has the considerable advantage of operating at ambient pressure and for moderate temperatures (1 bar, 25°C), with a lower cost and superior stability compared to hydrides in particular.

Claims

Claims

1. Porous composite for gas storage comprising: - a porous matrix comprising pores whose diameter is less than 10 nm, and - an organic compound comprising one or more electronegative atoms carrying at least one non-bonding doublet, such as oxygen 0, nitrogen N, fluorine F, chlorine Cl, bromine Br, iodine I, chosen from compounds capable of forming intermolecular hydrogen bonds, said porous composite being characterized in that said organic compound is present within said pores with a diameter of less than 10 nm

2. 11111. Porous composite according to claim 1 such that the pores of the porous matrix with a diameter of less than 10 nm represent at least 30%, preferably at least 50% of the micro- / mesoporous volume of the porous matrix.

3. Porous composite according to any one of the preceding claims such that said organic compound is chosen from the following compounds: polyphenols, polythiols, ureas, thioureas and calixarenes.

4. Porous composite according to any one of the preceding claims such that said organic compound is chosen from hydroquinone, resorcinol, fluorohydroquinone, 2-5 dihydroxyl-pyridine, catechol, urea, thiourea, calix[4]arene.

5. A porous composite according to any preceding claim such that said organic compound is present in crystalline, semi-crystalline and / or amorphous form within the pores.

6. Porous composite according to any one of the preceding claims such that the porous matrix is ​​chosen from organic or mineral micro- and / or mesoporous supports, such as silica, carbon, alumina, aluminosilicates, activated carbons, molecular sieves, zeolites, organometallic framework materials (Metal Organic Frameworks, MOFs), Hofmann clathrates and polymers.

7. Porous composite according to any one of the preceding claims such that the porous matrix is ​​chosen from meso- silicas porous MCM-41 and SBA-15, aluminosilicates, carbon xerogels, activated carbons and porous polymers.

8. Porous composite according to any one of the preceding claims such that the organic compound occupies at least 25%, preferably at least 40% of the micro- and mesoporous volume of the porous matrix.

9. A process for the dry preparation of a porous composite according to any one of the preceding claims comprising the adsorption / condensation of said organic compound in the gas phase within the pores of said porous matrix.

10. A method according to claim 9 comprising the prior step of sublimating said organic compound from the solid phase to the gas phase.

11. A method of storing gas comprising: - bringing the porous composite according to any one of claims 1 to 8 into contact with the gas to be stored or a mixture comprising said gas; - subjecting it to one or more successive temperature cycles.

12.

13. A method according to claim 11 such that the gas is dihydrogen. A gas storage device comprising the porous composite according to any one of claims 1 to 8, and further comprising a gas, said gas being stored within the pores comprising the organic material.

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